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26hp briggs running rough

E

ed will

Well-known Member
Hi, my older 26hp riding mower is running on 1 cyl. I put in new plugs. Any ideas what to check? Ed Will Oliver BC
 
Pull one plug wire at a time to find the missing cylinder, then see if there is spark on that cylinder, post back
 
I have heard comments about pushrod problems on Briggs engines, maybe pull the valve cover and take a look, once you verify which cylinder it is.
 
That could be a number of things.
#1 bad spark plug
#2 If it has the twin mags one mag could be bad
#3 Again if twin mag the shut down wire for one side maybe shorted to ground.
#4 problem with the intake from the carb
#5 low or no compression on one cylinder due to a valve problem or other such thing
#6 plug wire is shorted to ground
Me I would start by pulling the plugs out and look them over and then switch them to see if the flows the plug or if it does not. If it flows then you have a simple bad plug. If not then you will need to trouble shoot spark etc.
 
Go to the garden tractor forum and pull up page 5. Look for "Briggs V Twin RPMs Fluctuating ". Covers the problem quite in deapth. These engines can have a carburator problem that can lead to other problems. That revision #3 carb. works fantastically! !!
a168301.jpg
 
Bent pushrod. Been through it on a 24hp Briggs. It's no big deal to pull the valve covers and check. They're right out in the open.

My solution was to find a piece of steel tubing the that was an exact fit over the pushrods. Straightened the push rod and slipped a piece of tubing cut to the right length over the rod to reinforce it. (Left it about a half inch short on each end). Did it to all four. Switched to Mobil 1 oil and no problem since.
 
The valve covers are right out in the open with four small cap screws holding each one on. It's faster to pull the valve covers than to do a compression check.

Actually, just turning the engine over by hand will tell you if you have enough compression for it to run.
 
I thought I covered this yesterday but must have forget the submit step. The update on what Jeffcat said is on Tool Talk, date is Aug 2 and subject is "Jeffcat", authored by me.
 
(quoted from post at 15:16:04 08/07/17) Hi, my older 26hp riding mower is running on 1 cyl. I put in new plugs. Any ideas what to check? Ed Will Oliver BC
Click to expand...
My experience is 1) bent pushrod 2) mouse chewed plug wire.

On the pushrod the cause was the valve guide moved up from the head not allowing the rocker to go all the way down and bending the push rod. Replace 4 or 5 until a small engine forum put me on to the cause. I pushed it back in and used the corner of a chisel to go around it and set it in place. Been running that way for many years now.

Mice made a home under the shroud and chewed the wire from the mag to the plug. Was able to patch it until I could get a new mag with attached wire.
 
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